Electrosurgical devices utilize electrical current, such as radio frequency (RF) energy, to cut and cauterize tissue. Instruments for performing electrosurgery generally include an energy source, or generator, an active electrode for delivering electrical energy to tissue to be treated, a return electrode to complete the electrical circuit and conductors for coupling the energy source to the active and return electrodes.
Various types of open and closed surgical procedures utilize electrosurgical devices. Closed surgical procedures include arthroscopic, endoscopic, hysteroscopic, urologic, resectoscopic and laparoscopic procedures. For example, a hysteroscope is used in a closed surgical procedure for treatment of various conditions within a woman's uterine cavity. Typical uses of hysteroscopes include fibroid removal, intrauterine adhesion removal, endometrial ablation and correction of abnormal uterine bleeding.
The terms monopolar or bipolar can be used to characterize certain electrosurgical instruments. A monopolar electrosurgical instrument includes an active electrode for cutting tissue and a remotely located return electrode for providing a return current path. Bipolar instruments, on the other hand, are generally characterized by the return electrode being located in close proximity to the active electrode. The bipolar arrangement serves to restrict the area of current flow between the two electrodes, which may be desirable in certain applications, particularly where tissue damage is a concern.
Some surgical procedures, such as arthroscopic and hysteroscopic procedures, require distension of the surgical area in order to increase visibility at the treatment site or to minimize space constraints. In some instances, the surgical area is distended using a fluid.
An electrolyte-free (i.e., hypotonic) distension fluid is typically used in such procedures in order to prevent the electrical current delivered by the active electrode from dissipating to an ineffective level. However, absorption of excessive quantities of hypotonic solution into a patient's bloodstream can alter the patient's electrolyte levels and potentially result in dangerous conditions, including cardiac arrhythmia, brain swelling and even death. The risk of these dangers may cause the surgeon to terminate the procedure before completion. Furthermore, hypotonic solutions are expensive as compared to isotonic solutions.
The active electrode of electrosurgical instruments can take various forms. Exemplary active electrodes include conductive blades, conductive loops and conductive rollable cylinders (i.e., "rollers"). With conductive loops, the area of tissue contact is limited, thus requiring significant precision in manipulation of the electrode. While a roller provides a broader tissue contact area, which is advantageous in certain applications, its use has conventionally been limited to hypotonic fluid environments, in order to prevent undesirable dissipation of the current delivered by the conductive roller. This is because a significant conductive surface area of the roller which does not contact the tissue would conduct current to surrounding isotonic fluid and away from the treatment site.